Switch to SpeakEasy.net DSL

The Modular Manual Browser

Home Page
Manual: (v7man)
Apropos / Subsearch:
optional field

LD(1)                       General Commands Manual                      LD(1)

       ld - loader

       ld [ option ] file ...

       Ld  combines several object programs into one, resolves external refer-
       ences, and searches libraries.  In the  simplest  case  several  object
       files are given, and ld combines them, producing an object module which
       can be either executed or become the input for a further ld  run.   (In
       the latter case, the -r option must be given to preserve the relocation
       bits.)  The output of ld is left on a.out.   This  file  is  made  exe-
       cutable only if no errors occurred during the load.

       The  argument  routines  are  concatenated in the order specified.  The
       entry point of the output is the beginning of the first routine.

       If any argument is a library, it is searched exactly once at the  point
       it  is  encountered in the argument list.  Only those routines defining
       an unresolved external reference are  loaded.   If  a  routine  from  a
       library  references another routine in the library, and the library has
       not been processed by ranlib(1), the  referenced  routine  must  appear
       after  the  referencing routine in the library.  Thus the order of pro-
       grams within libraries may be important.  If  the  first  member  of  a
       library  is named `__.SYMDEF', then it is understood to be a dictionary
       for the library such as produced by ranlib; the dictionary is  searched
       iteratively to satisfy as many references as possible.

       The  symbols  `_etext', `_edata' and `_end' (`etext', `edata' and `end'
       in C) are reserved, and if referred to, are set to the  first  location
       above  the  program, the first location above initialized data, and the
       first location above all data respectively.  It is erroneous to  define
       these symbols.

       Ld  understands  several  options.   Except  for -l, they should appear
       before the file names.

       -s     `Strip' the output, that is, remove the symbol table and reloca-
              tion bits to save space (but impair the usefulness of the debug-
              ger).  This information can also be removed by strip(1).

       -u     Take the following argument as a symbol and enter  it  as  unde-
              fined  in  the  symbol table.  This is useful for loading wholly
              from a library, since initially the symbol table is empty and an
              unresolved reference is needed to force the loading of the first

       -lx    This  option  is  an   abbreviation   for   the   library   name
              `/lib/libx.a',  where x is a string.  If that does not exist, ld
              tries `/usr/lib/libx.a'.  A library is searched when its name is
              encountered, so the placement of a -l is significant.

       -x     Do  not preserve local (non-.globl) symbols in the output symbol
              table; only enter external  symbols.   This  option  saves  some
              space in the output file.

       -X     Save  local symbols except for those whose names begin with `L'.
              This option is used by cc(1)  to  discard  internally  generated
              labels while retaining symbols local to routines.

       -r     Generate  relocation  bits  in the output file so that it can be
              the subject of another ld run.  This flag  also  prevents  final
              definitions  from  being given to common symbols, and suppresses
              the `undefined symbol' diagnostics.

       -d     Force definition of common  storage  even  if  the  -r  flag  is

       -n     Arrange  that when the output file is executed, the text portion
              will be read-only and shared among all users executing the file.
              This  involves moving the data areas up to the first possible 4K
              word boundary following the end of the text.

       -i     When the output file is executed,  the  program  text  and  data
              areas will live in separate address spaces.  The only difference
              between this option and -n is that here the data starts at loca-
              tion 0.

       -o     The  name argument after -o is used as the name of the ld output
              file, instead of a.out.

       -e     The following argument is taken to be  the  name  of  the  entry
              point of the loaded program; location 0 is the default.

       -O     This  is an overlay file, only the text segment will be replaced
              by exec(2).  Shared data must have the same  layout  as  in  the
              program overlaid.

       -D     The  next argument is a decimal number that sets the size of the
              data segment.

       /lib/lib*.a      libraries
       /usr/lib/lib*.a  more libraries
       a.out            output file

       as(1), ar(1), cc(1), ranlib(1)